1. Field of the Invention
The present invention relates to a technique of suppressing periodic velocity fluctuations of a moving member.
2. Description of the Related Art
In a printing apparatus such as an inkjet printing apparatus, a carriage on which a printhead is mounted is generally moved by a driving mechanism using a motor as a driving source. A motor output contains a so-called torque ripple and cogging torque (to be generically referred to as cogging hereinafter) which are generated in a period corresponding to the motor structure. The cogging causes velocity fluctuations in the carriage in the same period as that of cogging. If printing is performed while velocity fluctuations occur in movement of the carriage, ink discharged from the printhead suffers a periodic landing error. This may lead to poor print quality such as image nonuniformity. A control technique for suppressing the influence of cogging has been proposed (for example, Japanese Patent Laid-Open Nos. 2000-232796 and 2010-052338).
The control method for suppressing the influence of cogging is feedforward control. When suppressing cogging by feedforward control, motor control data is corrected using correction data which is equal in period and amplitude and opposite in phase to cogging. Of these parameters, the cogging generation period is determined by the motor structure, as described above. The amplitude and phase need to be optimized for each product, and this requires a test operation to reciprocate the carriage several times. Even if these parameters are optimized before product shipment, their optimal values vary due to aged deterioration of the product and the like. Thus, the test operation is necessary after purchase by the user. If the test operation requires a dedicated time, the user has to wait because no print operation is performed quickly. Executing the test operation parallel to the print operation or the like may affect the print quality.